In practice, a hand-held camera will always shake a little. The movements will primarily be around a horizontal axis (yaw) and a vertical axis (azimuth or pitch). The magnitude of the movements will depend on the type of camera and other conditions, but will typically be in the order of ±0.15°.
The movements will normally have a frequency of up to 15 Hz. Movements in this frequency range can be compensated for by means of an image stabilization system. It is known to use one or more prisms or lenses to compensate for the movements and thereby stabilize the image.
U.S. Pat. No. 5,774,266 discloses an image stabilization system using a lens for deflecting the incoming radiation. The relative inclination between the optical axis of the photographic optical system and the optical axis 101a of the correcting lens 101 of the correcting optical mechanism which constitutes optical correcting means can be adjusted by causing an optical member to move in a plane perpendicular to or approximately perpendicular to the optical axis of an optical system, making the optical axis of the movable optical member eccentric with respect to the optical axis of the optical system. Adjustment means are provided to ensure that the optical axes are kept parallel.
WO 2007/091112 A1 discloses an image stabilizer comprising a prism. An optical image stabilizer is used to compensate for an unwanted movement of an imaging system, such as a camera. The camera has a folded optics system using a triangular prism to fold the optical axis. Two actuators are used to rotate the prism around two axes in order to compensate for the motion of the camera.
U.S. Pat. No. 6,370,329 discloses a camera in which two pivotable mirrors are used to deflect the incoming radiation in order to provide image stabilization. The mirrors are controlled in dependence of gyro signals.
For visible light cameras solutions are known in which the image detector itself is moved to compensate for the movement of the camera. This is not feasible for IR cameras since the sensor array in such cameras typically requires cooling.